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Forecasting for Public Policy (



A talk to Institute of Economic Affairs summer interns at King's College London. [ redirects here. Related research is listed below the following slideshow.]
Forecasting for Public Policy
Kesten C. Green
University of South Australia Business School
& Ehrenberg-Bass Institute
Institute of Economic Affairs
11AM12:30PM, Thursday 10th July 2014
Pyramid Room K4U.04, Kings Building
King’s College London
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Outline of the talk
1. Needs for forecasting
2. Evidence-based forecasting
3. Golden Rule of Forecasting
4. Commercial speech control
5. Forecasting for climate
6. Q&A
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Objectives of the session
1. Introduce evidence-based or
scientific forecasting
2. Introduce the Golden Rule of
Forecasting Checklist
3. Describe 2 public policy
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The fatal conceit
1. The knowledge problem
2. The chess pieces fallacy
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Chess pieces fallacy
Adam Smith commented on the theorist
“…seems to imagine that he can arrange
the different members of a great
society with as much ease as the hand
arranges the different pieces upon a
chess-board.” *
*Adam Smith (1976). The theory of moral sentiments.
Liberty Classics: Indianapolis
Hayek on regulation
It was only when, because the economic system did not
accomplish all we wanted, we prevented it from doing what
it had been accomplishing, in an attempt to make it obey
us in an arbitrary way, that we realised that there was
anything to be understood. It was only incidentally, as a
by-product of the study of such isolated phenomena, that it
was gradually realised that many things which had been
taken for granted were, in fact, the product of a highly
complicated organism which we could only hope to
understand by the intense mental effort of systematic
inquiry. Indeed, it is probably no exaggeration to say that
economics developed mainly as the outcome of the
investigation and refutation of successive Utopian
proposalsif by ‘Utopian’ we mean proposals for the
improvement of undesirable effects of the existing system,
based upon a complete disregard of those forces which
actually enabled it to work.
Needs for forecasting*
1. Future without policy is uncertain
2. Effects of proposed policy is
3. Effects of alternatives are uncertain
4. Forecasts for all costs and benefits
over long term are needed
5. Independent auditing of forecasting is
6. What is the alternative?
*For private sector, and for public when fatal conceit is
** ”Unintended consequences. 7
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The best and the brightest
Group 1 consists of the best and
brightest experts in the world. They
know much accurate and relevant
Group 2 consists of intelligence
people. They have some relevant
knowledge and information.
Which group would produce the most
accurate forecasts?
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Experts vs. novices for forecasting in complex
uncertain situations
Group 1 would do…
no better
…than Group 2.
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Evidence on accuracy of
unaided judgments by experts
Seer-sucker theory: “No matter how much
evidence exists that seers do not exist, suckers will
pay for the existence of seers” (Armstrong 1980;
based on a literature review).
Expert political judgment (Tetlock 2005)
284 experts made 82,361 forecasts of political,
social and economic developments over a 20-year
They were little more accurate than novices.
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The Seer-Sucker Immunity
Everyone knows that they and their
favorite seers are immune from…
…Just as everyone is above average.
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So what?
Surveying experts’ opinions about what
will happen in the distant future is
…even when the implications of their
opinions are analyzed by computers.
What is the alternative?
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The alternative:
Evidence-based forecasting
Use evidence-based methods
(Analogous to evidence-based medicine)
Fortunately, researchers have been
conducting experiments on how to forecast
under given conditions for nearly a century
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Forecasting principles project
From 1995 to 2000
Papers by 40 internationally recognized
forecasting experts
Reviewed by another 123 leading
experts on forecasting
Led to 139 “principles of forecasting”
published as a handbook in 2001
Principles summarized by the
Forecasting Audit freeware
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A unifying theory for forecasting
139 principles (now 140) is a lot
Too many for polic y d e v e lop m e n t ?
Is it possible to simplify?
We (Armstrong, Green, & Graefe)
propose a unifying theory of forecasting…
The Golden Rule of Forecasting
…to make evidence-based forecasting
more accessible to forecasters &
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Golden Rule of Forecasting is to
Be Conservative
Use cumulative knowledge on the situation
Subject matter expertise moderated by
experimental evidence
Long-run relationships
Trend s
Use cumulative knowledge on evidence-based
forecasting methods
* Or
Forecast unto others as you would have them
forecast unto you.
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Are Golden Rule violations
easily spotted?
Yes, if the description of the forecasting
methods is adequate.
The Golden Rule of Forecasting Checklist
software can be used by novices following a
short preparation.
If the method description is not adequate, the
Golden Rule has been violated.
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When to be conservative
For all forecasting problems.
Especially important if situation is
Bias is likely
A common conjunction in forecasting for
government policies
investment proposals
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Example of a complex uncertain
situation with biased forecasting
Demand forecasts for 24 large rail
transportation projects are
consistently optimistic, with a
median overestimate of 96 percent
for traffic (Flyvbjerg 2013).
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Conservative extrapolation guidance
Modify trends, if the…
a.series is variable or unstable
b.historical trend conflicts with causal
forces (contrary series)
c.forecast horizon is longer than the
historical series
d.short and long-term trend directions
are inconsistent
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Conservative causal model checklist
1. Use prior knowledge to select important
variables and estimate effects
2. Moderate effect estimates to reflect
3. Use all important variables
4. Combine models that use different
information, procedures.
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Conservatism via combining
across methods & forecasters
Incorporates more prior knowledge
Reduces effects of:
Data errors
Computational errors
Model selection errors
Biased judgments
Error reductions, under ideal conditions,
exceed one-half (Graefe et al 2014)
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Experimental evidence on the
Golden Rule
Found 150 experimental
comparisons so far
Number of comparisons supporting
vs rejecting the Golden Rule,
Violating a guideline will typically
increase error by half again.
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Common causes of Golden Rule violations
A. Big data: Why so?
1. Encourages evasion of a priori analysis.
2. Includes irrelevant variables.
B. Complex statistical procedures: Why so?
Regression analysis of non-experimental data
on complex situations is invalid, no matter
what the sample size (Armstrong, Illusions
in regression analysis)
We were unable to find a single experimental
comparison showing that using complex methods
on big data improves forecast accuracy versus
reasonable alternatives.
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Barriers to adoption of the Golden Rule
Expensive: Need to use comprehensive prior
knowledge about relationships and
forecasting methods
Unimpressive:Methods are easy to understand
Boring: Forecasts not newsworthy (e.g.
Clients pay for impressive, obscure, complex
methods, and stories based on
unaided expert opinions.
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GR checklist can be used by novices to
identify forecasts that violate the
Golden Rule
The simplicity of the Guidelines and the
use of checklists* gives clients the ability
to assess the worth of forecasts in a rapid
and inexpensive way.
If the method is too complex to
understand, give it a failing mark.
*Our paper summarizes the evidence on the
value of checklists.
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Possible action steps
A. Apply the Golden Rule Checklist to a
forecasting problem with which you are
familiar? How many of the 28 checklist items
were violated?
B. Consider a public policy issue, such as
Will government mandated messages and
images on cigarette packs increase consumer
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If you have suggestions for improvements,
contact Andreas Graefe (
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Further information
For latest versions of…
1. Slides
2. Golden Rule of Forecasting working paper
3. Golden Rule of Forecasting Checklist
(available on paper, as Excel Sheet, and as an online tool)
5. Data on error increases from ignoring
All at
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Golden Rule can be unpopular as a
constraint on dramatic forecasts
Applying complex statistical methods to
non-experimental data violates the Golden
Rule by ignoring knowledge about the
situation and forecasting methods.
Violating the Golden Rule of Forecasting
increases forecast errors enormously
Violating a typical guideline increases error
by half again.
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Effects of government
mandated messages
(particularly disclaimers)
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Disclaimers fail to work as intended
Failure arises because disclaimers
relate to matters that are not vital for
the customer’s decision-making
include negation (negative words)
are based on opinion or tentative
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Florida Statutory Disclaimer
There are two logical interpretations, one of which
seems unusual.
(1)It is a true statement if we substitute other
organizations (e.g. “Institute of Economic Affairs”) for
(2)The AAID is not bona fidethe common
interpretation, and that constitutes false advertising.
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Why an experiment
rather than a survey?
Concern is effect of disclaimer on decision
How much improvement in net welfare?
Experiments are the only feasible way to assess
Surveys can show people are confused by
This has been well-known since the advent of
advertising surveys
Particularly with disclaimers and corrective ads
But surveys cannot assess the effects of a
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Field work
Field work supervised by Gallup & Robinson
They were not told the identity of the
They made suggestions on the wording
of the questions.
Experiment administered by CRG Global,
Florida (who also did not know client)
In malls in Orlando, Daytona Beach, and
Fort Lauderdale.
They trained the interviewers.
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Why face-to-face rather than
telephone interviews?
People read the ads and disclaimers
Best practice
When tangible item such as an ad needs to be
»Jacoby and Handlin (1991)
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Is it proper to generalize from
experiments with convenience samples?
Yes, it is proper. All of the famous experiments (e.g., Milgram)
have been done with convenience samples. Same for medical
In addition, it is consistent with research on this:
• Findings from experiments on students, yield valid results
Are appropriate for experiments on decision making (DM)
Close match between lab and field*
Accounting DM processes**
Managerial DM***
*Locke 1986; **Liyanarachchi and Milne 2005; ***Remus
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Has the experimental approach been
used as evidence in similar court cases?
Berlex Labs vs Schering AG
Use of disclaimers for Berlex drug (Berlex not
related the Schering AG)
Convenience sample of physicians and
pharmacists for experiment by Berlex
Schering AG commissioned a representative
sample experiment
Findings supported the original conclusion
(From Jacoby and Szybillo 1994)
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Random assignment to
experimental treatments
Participants (subjects) shown two mock Yellow Pages ads
for implant dentists…
-Dr Alan Reed (AAID credentials shown)
-Dr Barry Smith (no AAID credentials shown)
…and asked (Q1) to recommend one of the dentists to a
friend in need of implant dental work and (Q11) which
one is better qualified to do implant dentistry?
Randomly assigned to receive the Dr Smith ad…
and a Dr Reed ad with one of the treatments:
• No disclaimer.
• Disclaimer required by Florida law
• A “modified” disclaimer
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Dr Alan Reed DDS
General Dentist
Fellow, American Academy of Implant Dentistry
Diplomate, American Board of Oral Implantology/Implant Dentistry
Implant dentistry is a technique by which artificial replacement teeth are
fastened to metal posts surgically implanted in a patient’s jaw bones.
Note: Implant dentistry is not recognized as a specialty area by the American
Dental Association or the Florida Board of Dentistry. The AAID is not
recognized as a bona fide specialty accrediting organization by the American
Dental Association or the Florida
Board of Dentistry.
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Dr Barry Smith DDS
General Dentist
Implant dentistry is a technique by which artificial replacement teeth are
fastened to metal posts surgically implanted in a patient’s jaw bones.
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Definition of less-qualified
In the experiment, the dentist
who did not advertise
qualifications (Dr Smith) was
“less-qualified,” because ads
present best arguments.
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Why assume those with AAID
certificates are more skilled?
Dentists with AAID credentials have
been subject to bona fide training and
Our experiment gave the choice
between a dentist with training and
one without
It is reasonable to assume that
someone who advertises training is
more skilled than one who does not
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What can you say about the
training provided by AAID?
The process
Learner responsibility
Experiential learning with skilled practitioner
Tes t sk il ls and knowledge
Requires substantial study
Conforms to best practice for training
“Learner Responsibility in Management Education, or
Ventures into Forbidden Research Interfaces 1983.
“Designing and Using Experiential Exercises,” in M. W.
DeLozier et al., Experiential Learning in Marketing
Education 1977.
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Recommend dentist to a friend
This is a survey about implant dentistry. That’s a
technique in which titanium metal posts are
permanently embedded in the patient’s jaw in a
series of surgical operations, and false teeth are
attached to the posts.
Please imagine that you have a friend who needs
implant dentistry. You find these two
advertisements in the Yellow Pages.
Please read these two Yellow Pages
advertisements carefully.
Q1 Please tell me, which of these dentists would
you recommend to your friend?
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Selection of less-qualified dentist
When the FSD was used…
Inferior decisions were made by 1.6
times more people:
21% recommended the less-qualified Dr Smith
when FSD was used (n=100)
13% recommended the less-qualified Dr Smith
when FSD was not used (n=112)
Note: If there had been no improvement in decisions, there
would be no basis for the FSD. In practice, decision making
was harmed.
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Re-test of decision making (Q11)
A remarkably similar result for the
alternative way we posed the question:
Q11 Which of these dentists do you think is
better qualified to do implant dentistry?
Inferior judgments were made by 1.6 times
more people when the FSD was used:
19% erroneously judged Dr Smith was better-
qualified when the FSD was used
12% erroneously judged Dr Smith was better-
qualified when the FSD was not used
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Is an increase in poor decisions
from 13% to 21% important?
It shows people make worse, not
better, decisions when exposed to the
Effect is large:
Nearly 10% of those who would have
chosen a qualified dentist were
induced to chose an unqualified one
by the FSD
FSD is not justified, adds to costs,
harms suppliers, harms customers.
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Retaining ads increased
inferior judgments (Q11)
When the FSD was retained…
Inferior judgments were made by 1.3 times
more people than when it wasn’t
22% erroneously judged Dr Smith was better-
qualified when FSD was retained (n=51)
16% erroneously judged Dr Smith was better-
qualified when FSD was returned (n=49)
The greater the exposure to the FSD the worse the
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Effect of FSD on
less-educated people’s decisions
When exposed to FSD, people without a
college degree were about 1.5 times more
likely to make a poor decision than college-
educated people.
25% without college degree (n=48) made poor
16% with college degree (n=50) did so
Without FSD, education had no effect on
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Effect of FSD on women’s decisions
Women exposed to the FSD were
1.8 times more likely to make a
poor decision than men
• 28% of women (n=46) made poor
• 15% of men (n=54) did so
Without FSD, women made similar
decisions to men
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Majority of subjects did not understand
organizational arrangements after
exposure to FSD
Recognized as specialty by ADA 68
Recognized as specialty by FDB 67
Recognized as accrediting body by ADA 64
Recognized as accrediting body by FDB 60
We measured only short-term effects. Another
experiment showed an effect opposite to the intention
of a disclaimer after 3 days*
*Skurnik, Ian, C. Yoon, D.C. Park & N. Schwarz (2005)
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FSD also imposes
costs on suppliers
FSD imposes costs on dentists who want
to inform prospective patients about their
credentials by
• reducing the effectiveness of their
• increasing the cost of the ads
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Might a modified disclaimer work?
We tried to add clarity and to
remove the false statement, but
could not resolve two problems:
1)the organizational arrangements
are irrelevant to customers
2)“not” was unavoidable
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The modified disclaimer
“The American Academy of Implant
Dentistry (AAID) provides education,
training and testing in implant
dentistry. The AAID is the oldest U.S.
organization offering credentials in
the field. It is independent of the
American Dental Association, which
does not provide training or
certification in implant dentistry.
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Modified disclaimer did not work
Our attempt was not successful
15% who saw modified disclaimer made an inferior
(vs 13% when no disclaimer)
Prior research shows disclaimers are hard to
Listerine, same % misunderstood corrective message
whether written by the company or the FTC (Mazis
and Adkinson 1976)
Is it possible to write a disclaimer that would
help consumers in this situation?
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“Commercial” speech restrictions:
Experimental evidence, and principle
Discuss other evidence and principle…
For details, see
Green, K. C. & Armstrong, J. S. (2012). Evidence on the
effects of mandatory disclaimers in advertising. Journal
of Public Policy and Marketing, 31, 293304. [With
commentary, 305324]
Armstrong, J. S. & Green, K. C. (2012). Should we put
a price on free speech? Journal of Public Policy and
Marketing, 31, 325.
Green, K. C. & Armstrong, J. S.(2012).Have the courts
protected free speech for business people? JPP&M
Internet Appendix.
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Global temperatures, long term:
Most important forecasting
problem of our time
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§Global warming described as the
“greatest moral problem of our time”
by former Australian PM Kevin Rudd
§Proposed policy responses very expensive
§Policy proposals based on explicit and
implicit forecasts
Conclusions from evidence-based
forecasting for global warming
Policies rest on forecasts of (1) climate, (2)
climate effects, and (3) policy effects
None are scientifically valid forecasts
Violate relevant forecasting principles
Violate the Golden Rule of Forecasting
Validation studies show GW forecasts to be
GW is an anti-scientific political movement…
similar to other manmade disaster alarms
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Global warming policies and the
requirement for forecasts
Rational policies require accurate forecasts from
validated evidence-based methods which
determine that:
1.Global warming will occur over the long term
2.Substantial welfare loss will result from
3.Policies will reduce net welfare loss
All three are necessary
To date, there is n ot a single sci e n t i f ic forecast
supporting any of the three.
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No scientifically valid forecasts
for global warming
Based on our forecasting audit, the IPCC
forecasts violated 72 of the 89 relevant principles,
failing to:
1. Provide full disclosure of methods and
2. Assess reliability and validity of the data
3. Compare forecasts from different
4. Be conservative,especially in situations
of high uncertainty and complexity.
See: Global Warming: Forecasts by Scientists
versus Scientific Forecasts
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No scientifically valid forecasts for
detrimental effects of global warming
Are we currently at the optimum
Is warming more harmful than
Is warming more likely than
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No scientifically valid forecasts for
cost-effective policies
Two governme nt fore ca sting rep orts supported listing
polar bears as endangered
Findings: Fewer than 14% of relevant forecasting
principles were properly applied
Forecasts of up to 100 years were made based on an
analysis of data from five (consecutive) years
Bias: “USGS Science Strategy to Support US Fish and
Wildlife Service Polar Bear Listing Decision”
Refusal to provide the data used
Source: Polar Bear Population Forecasts; Senate
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Do the IPCC forecasts
follow the Golden Rule?
Aware of the IPCC procedures, Green and
Armstrong and independently checked them
against the GR Guidelines “Checklist”
Notice the parallel to medicine where checklists
have saved many lives
You can do that yourself now that you know
where to find the checklist. It took us 10
minutes each.
25 of the 27 guidelines judged to be relevant
Of these, IPCC forecasts violated 25
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Why do forecasters violate the
Golden Rule?
Use forecasts as a planning
document to motivate behavior
Free to create any plan they like
Forecasts restricted to determining
what will happen given the plan
otherwise it is senseless
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People also violate the Golden
Rule because “Things are different
How do we know they are
Opinions of some experts
Be skeptical of this belief
As Eisenhower said, “Things are
more like they are now than they
ever have been. 70
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Global temperature
Please forecast the
missing years for the
series shown on the
two charts, each for
50 years
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Results from the professional
The graphs are nearly identical, so
how can they claim that the situation
is unique?
Half of them predicted increased
temperatures for both.
Series A temperatures actually went
So far, series B temperatures are
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(Source of concept: W. Meyer 2009)
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Forecasting trends
A trend is a trend is a trend.
But the question is, will it bend?
Will it alter its course through some unforeseen
force and come to a premature end?
Golden Rule Guidelines:
Lacking clear causal support, damp the
If the causal forces are contrary with the
trend, forecast no trend. (The Simon-Ehrlich
bet was the most famous application of this
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Validation studies: Armstrong-
Gore “Bet
Armstrong proposed bet to Al Gore to
demonstrate the need for proper validation
studies. (Motivation: Julian Simon and his bet
with Ehrlich and Holdren).
10 years for Global Mean temperature
Gore: “tipping point” or even “too late”
Armstrong: 10-years is too short
At the start, Gore would have a chance to
win based on
random variation
Updated monthly at
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Long-term validation study on
global warming
To f orec ast und er hig h co mple xit y and uncertainty,
use the no-change “benchmark model.
We tested that against the forecast used by the
IPCC (0.03°C-per-year), using UK Met Office Hadley
Centre’s annual average temperature data, 1850-
For long-term forecasts (1 to 100 years ahead), the
no-change model’s forecast errors were 1/7of the
IPCC model’s (7,550 predictions).
For horizons 91 to 100, the no-change model’s
errors were 1/12 of the IPCC models.
Source: Green, Armstrong & Soon (2009)
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Possible improvements in global
mean temperature forecasting
1. Improve “nowcasting” (starting year
contains measurement error)
2. Adjust for known biases in the Hadley data
3. Use alternative data sets
4. Consider damped trends for short-term
5. Combine evidence-based forecasts
However, the no-change model provides
forecasts sufficiently accurate for policy
e.g. MAPE of 50-year-ahead forecasts =
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Recent progress in
global mean temperature forecasting*
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*Green & Armstrong in “Climate change: The facts 2014”, IPA.
Available from
Evidence-based climate forecasts
for the 21st Century
Each year’s global average temperature for the 100
years to 2113 will be the same, more or less, as
the 2013 figure
Monitor against the University of Alabama at
Huntsville’s (UAH) lower troposphere temperature
satellite-based better assessment of the global
average than HadCRUT3
fully and openly documented
therefore, less likely to be biased
Our chapter for the IPA Facts book provides good
news: There is neither need to worry about climate
change, nor reason to take action.
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Short-term validation of our
polar bear population forecast
Described as a “tipping point” in the January 2008
U.S. Senate endangerment hearing… rapid decrease in
population forecast by polar bear scientists.
Armstrong, Green, and Soon report for Alaska
government and subsequent paper forecast that polar
bear population would increase in the short-run, then
level off.
Evidence since the hearings suggests that the polar
bear population has increased. (Mitch Taylor,
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Conclusion: Global warming
movement is based on an anti-
scientific forecast of manmade
We then forecast the outcome of this
movement by using “structured analogies”
Julian Simon had originally used analogies
to show that the global warming movement
was a common social phenomenon (also
Madness of Crowds, etc.)
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Use of analogies in forecasting
Often used to sell a forecast, but no
value for accuracy.
Structured analogies seeks analogies
and then a clerk makes forecasts
based on what happened.
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Structured analogies procedure
1. Generate analogies:
Asked experts to describe analogies to the current
dangerous manmade global warming alarm; reviewed
the literature
2. Assess similarity:
Consulted published sources and assessed proposed
analogies for similarity to the target AGW situation;
selected those that met predetermined criteria
3. Thumbnail sketches:
Prepared brief descriptions of the analogies
4. Assess outcomes:
Obtained evidence analogies’ outcomes from published
5. Forecast for target:
Derived forecasts about Global Warming Alarm from
modal analogy outcomes
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Evidence on structured analogies
Conducted a validation study using 8 conflict situations
Example:Artists Protest (Chance: 17%; UJ: 10%; SA2+: 50%)
Findings from 97 structured analogies forecasts and 106 unaided
expert forecasts :
Method % accurate
Guessing 28
Expert unaided judgment 32
SA with two or more analogies 56
Source: Green and Armstrong (2007)
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Analogies to Global Warming
71 analogies proposed (literature;
26 met criteria
Harm physical environment
None were based on scientific evidence
Government actions recommended in
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Examples of analogies to
global warming
1. Uncontrolled reproduction and
degeneration (eugenics) 1883
2. Soil erosion threat to agricultural
production 1934
3. DDT and cancer 1962
4. Population growth and famine 1968
5. Global cooling 1975
6. Electrical wiring and cancer 1979
7. Mercury in fish 2004
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Outcomes of the analogies
Governments took action in 23 of the 26 analogies
• None of the predicted outcomes came true
Movements gradually faded
• Government expenditures remained
GW is part of common social phenomenon and, like the
others, will slowly fade, but the harmful costs to
society will continue.
Source: Green and Armstrong,
Effects of the Global Warming Alarm” (2011)
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What Simon said in 1992
Julian Simon claimed that
environmental alarmists are
motivated by political rather than
scientific objectives.
He concluded that doomsayers’
forecasts were always wrong and
that the environment keeps getting
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